New places to build more factories.

Transportation of the player, be it vehicles or teleporters.

New ways to deal with enemies, be it attack or defense.

Changes to enemies or entirely new enemies to deal with.

Map generation and terrain modification.

New Ores and resources as well as machines.

Things related to oil and other fluids.

Furnaces, assembling machines, production chains.

Changes to power production and distribution.

More than just chests.